Basic HTML Version
Molecular Soil Biology (online), 2013, Vol. 4 No.2, 7-15
ISSN 1925-2005
http://msb.sophiapublisher.com
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Earthworm activity in soil, transfer minerals to
different horizons and also organics to lower horizons
of soil (Rahmani and Saleh Rastin, 2000). Creation of
holes in path of earthworms increases water
penetration and soil aeration. It has been shown that
60% of earthworm's paths at soil depth of 15 cm and
18% of earthworm's paths at soil depth of 80 cm have
been covered by tree roots (Rahmani and Saleh Rastin,
2000). Results of some studies on castings (worm
dung) indicate abundance and diversity of fungal
species (Groffman et al., 2004); bacterial plate counts,
moisture content and concentrations of soluble
organic-C are higher than the adjacent soil (Valckx et
al., 2006). Moreover, most of the physico-chemical
characteristics of castings are more than those of the
underlying soil in both arable and natural vegetation
areas. Earthworms have the highest biomass of earthen
invertebrates. Also they cause remarkable increase in
soil microorganisms and have an important effect on
soil invertebrate's diversity and feed cycle (Rahmani
and Saleh Rastin, 2000; Groffman et al., 2004).
Natural disturbances represent the key factor in
natural forest dynamics (Frelich, 2002; Janasova et al.,
2010). In the concept of disturbance ecology,
disturbances are considered as an important part of
soil ecosystem and plant communities dynamics
(Samonil et al., 2009; Kooch and Hosseini, 2010). The
most important type of disturbsnces in the temperate
forests is blowdowns connected with the direct
disturbance of soils (Kooch et al., 2010). Tree
uprooting has important influences on forest ecology
and implications for forest management (Phillips et al.,
2008). Trees uprooting and pit and mound landscape
creating is in general more likely in shallower and
wetter soils, or where restrictive horizons limit root
penetration. However, the size of trees seems to be
more important than soil characteristics with respect
to both the likelihood of uprooting and the amount of
soil disturbed (Peterson, 2007). In general, consistent
positive relationships exist between tree diameter and
blowdown risk, and uprooting and wind damage
varies among species, related to wood strength,
rooting habit, and other factors. Shallow rooting
increases wind throw vulnerability (Phillips et al.,
2008). With considering mountainous position of
hyrcanian forests in northern Iran and presence of
trees with high diameters (old trees), therefore, it is
imagined that many of trees are prone to uprooting by
windthrow event.
It is now well known that forest disturbances
generally result in significant variability of earthworm
populations in temperate landscapes (Hendrix and
Bohlen, 2002; Kooch and Hosseini, 2010) with
significant ecological implications for ecosystem
functioning (Barros et al., 2004; Gonzalez et al., 2006).
Consequently, earthworms should serve as good
indicators of environmental changes that occur by
disturbance (Decaens and Jimenez, 2002; Tondoh et
al., 2007; Kooch and Hosseini, 2010). Relationships
of earthworms and soil properties have been
well-documented for agricultural systems (Lamande et
al., 2003; Decaens et al., 2004; Winsome et al., 2006)
and forests (Whalen, 2004; Marhan and Scheu, 2005;
Heneghan et al., 2007). In comparison, few studies
have examined the density and biomass of earthworms
in disturbed soils (Kooch and Hosseini, 2010). Up to
now, however, only few studies (Haynes et al., 2003;
Dlamini and Haynes, 2004) have simultaneously
studied changes in earthworm communities and soil
parameters, in response to forest disturbance in Iran
(Kooch and Hosseini, 2010). It is not clear whether
earthworm populations are mainly controlled by the
amount of food, its quality, or the chemical properties
of their environment (Aubert et al., 2003; Scheu et al.,
2003; Gonzalez et al., 2003). Therefore, determining
the relation among earthworm's biomass and diversity
with created microsites by uprooting trees (pit and
mound landscape) and edaphic conditions are essential
for management of forest ecosystems. The present
study is intended to address these issues by: (i)
assessing the impact of forest disturbance on
earthworm assemblages along a gradient of pit and
mound landscape, and (ii) identifying soil variables
associated with changes in earthworm abundance and
diversity. Specifically, two main hypotheses were
tested: (i) earthworm communities significantly
change along the pit and mound landscape and, (ii)
soil water content is the main driver of earthworm
assemblage change.